linux-kernel - Re: [PATCH] printk: Remove superfluous memory barriers from printk

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Message-ID: <20171012093442.GC2882@pathway.suse.cz>
Date:   Thu, 12 Oct 2017 11:34:42 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH] printk: Remove superfluous memory barriers from
 printk_safe

On Wed 2017-10-11 12:46:47, Steven Rostedt wrote:
> From: Steven Rostedt (VMware) <rostedt@...dmis.org>
> 
> The variable printk_safe_irq_ready is set and never cleared at system
> boot up, when there's only one CPU active. It is set before other
> CPUs come on line. Also, it is extremely unlikely that an NMI would
> trigger this early in boot up (which I wonder why we even have this
> variable at all).
> 
> Also mark the printk_safe_irq_ready as read mostly, as it is set at
> system boot up, and never touched again.
> 
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

Great catch! It makes perfect sense:

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr